Castro said the U.S. government contractor arrested in Havana on Dec. 5 was supplying opposition groups with “satellite communication equipment” that is banned in the Caribbean country.

“The enemy is as active as ever, as demonstrated by the detention in recent days of a U.S. citizen,” Castro told the country’s National Assembly in Cuba’s first comment on the American’s detention.

“The U.S. government has not renounced the destruction of the revolution ... (and) in recent weeks we’ve been witnesses to a multiplying of such efforts by the new administration,” said Castro, 78, who took over the presidency from his ailing older brother Fidel, 83, early last year.

U.S. President Barack Obama promised this year to “recast” Washington’s relationship with Cuba and took initial steps such as lifting restrictions on family visits and slightly softening the 47-year-old trade embargo on the island.

A warmer atmosphere led the Cold War-era foes to resume migration talks in July and Cuba welcomed a different attitude at the White House.

However, Fidel Castro, who has not been seen in public since 2006, has been increasingly critical of Obama in recent weeks. Political analysts say the arrest could set back Obama’s efforts to thaw ties but is unlikely to cause lasting damage.

Despite criticizing Washington on Sunday, Raul Castro said his government remained open to better relations as part of a “respectful dialogue.”

CELLPHONES

The U.S. State Department has confirmed the arrest of the unidentified American, who The New York Times reported was handing out laptops and cellphones on the island.

Raul Castro has ended previous curbs on ordinary Cubans using cellphones and computers, but satellite phones and walkie-talkies are banned, while Internet access is heavily controlled.

He did not say exactly what kind of satellite equipment the arrested man had been distributing.

Politico journal, quoting sources in the U.S. Congress, said he was a subcontractor for U.S. government aid agency USAID who was giving out cellphones and flash drives and was arrested at Havana airport as he prepared to leave Cuba.

Maryland-based Development Alternatives Inc, which says it has a federal contract to support “just and democratic governance in Cuba,” has described the man as a sub-contractor employed “to assist Cuban civil society organizations”.

These Cuban dissident groups are termed “mercenaries” and “traitors” by the Cuban government, which has often accused the United States of supporting them openly and also covertly in a bid to undermine the one-party communist system.

U.S. diplomats have asked to see the detained man, but a spokeswoman for the U.S. Interests Section in Havana said on Sunday they were still waiting for a response from Cuba.